This invention relates to nuclear reaction material storage and, more particularly, to an annular tank for storing nuclear reaction material and a method of fabricating the annular tank for storing various types of nuclear reaction material dissolved in a solvent.
There is a solvent extraction method as one of the methods of wet reprocessing spent nuclear fuel in a nuclear fuel cycle (an outpile fuel cycle). The method essentially handles water soluble nuclear reaction materials such as uranium U, plutonium Pu, thorium Th dissolved in a solvent such as nitrate or the like and employs an annular tank as one container for storing the fuel liquid.
The conventional annular tank thus used in the method of reprocessing spent nuclear fuel is constructed to form a annular space to contain reaction material by annular upper and lower dies (with an inlet hole) disposed in space, and inner and outer sheaths extended at the inner and outer peripheries of both the dies. This tank must be precisely produced in the same manner as various devices and equipment in the nuclear reaction field so that even an accidental radiation leakage cannot occur resulting in a large sacrifice in production, technical working, efficiency and cost.
It has heretofore been proposed, for the purpose of alleviating the aforementioned problems to some degree, to produce an annular tank using the steps of dividing a blank of an upper die into segments by means of pressing and cutting operations, forming the upper die by welding the segments, forming a channel-shaped lower die by pressing a plate blank to thus reduce material of the upper die, to alleviate the difficuty in the production technique, to enhance the working efficiency, and to simplify the production of the lower die.
The upper die can thus be enhanced in accuracy upon fabrication of the segments, however another problem occurs when welding the segments such as thermal deformation at welding time, deflection caused by the thermal work together with an apprehension of cracks at the welded portions. In addition, since the lower die is made of thin plate plate, it accommodates low thermal capacity to cause feasible strain at the inner and outer sheaths at welding time which finally results also in difficulty in accuracy with regard to passing a non-destructive inspection by external appearance, size and X-ray irradiation.